Melanochromis mpoto Konings & Stauffer, 2012, new species

Melanochromis mpoto new species (Figs. 5 & 6; Table 4) Melanochromis ‘blue’ Ribbink et al. 1983 Melanochromis robustus (non Johnson) Konings 1995 Melanochromis benetos (non Bowers & Stauffer) Schraml 1998 Melanochromis spec. ‘Matema’ Schraml 1998 Holotype. PSU 6039, 86.6 mm SL, male; Malaŵi, Lake Malaŵi, Katale Island, 10 ° 27.3 ' S, 34 17.2 ' E, A. Konings, 10 Oct 2009. Paratypes. PSU 6040, 3, 66.9–91.1 mm SL, data as for holotype; PSU 6041, 7, 50.9–67.4 mm SL, Malaŵi, Lake Malaŵi, Chitande Island, 10 ° 23.8 ' S, 34 ° 15.3 ' E; A. Konings, 8 Oct 2009; BMNH 2012.1. 31.1.1, 1, 74.0 mm SL, male, data as for holotype; BMNH 2012.1. 31.1.2, 1, 53.7 mm SL, female, Malaŵi, Lake Malaŵi, Chitande Island, 10 ° 23.8 ' S, 34 ° 15.3 ' E, A. Konings, 8 Oct 2009; AMNH 255292, 1, 85.4 mm SL, male, data as for holotype; AMNH 255293, 1, 55.8 mm SL, female, Malaŵi, Lake Malaŵi, Chitande Island, 10 ° 23.8 ' S, 34 ° 15.3 ' E, A. Konings, 8 Oct 2009. Diagnosis. Females and non-breeding males of M. mpoto are distinguished from all congeners, except M. melanopterus, M. vermivorus, and M. baliodigma, by a dark brown body and a melanin pattern, when discernible, consisting of two dark horizontal stripes combined with dark vertical bars. The only other Melanochromis species with such a pattern is M. baliodigma, but M. mpoto can be distinguished from the latter species by having vertical bars that are narrower than either horizontal stripe; in M. baliodigma the vertical bars are much wider than the horizontal stripes. Mouthbrooding females of M. robustus can exhibit vertical bars as well, but this species has a greater interorbital width compared to that of M. mpoto (26.1–29.6 % HL vs. 14.8–21.8 % in M. mpoto). Melanochromis mpoto differs from M. melanopterus and M. vermivorus by a shallower cheek depth (15.4–21.7 % HL vs. 22.9–31.7 % HL in M. melanopterus and 28.2–36.2 % HL in M. vermivorus). Male M. mpoto in breeding colouration are light blue/blue without any bars or stripes visible on the flank. Melanochromis mpoto males are thus distinguished from those of most other Melanochromis species except M. lepidiadaptes, M. kaskazini, and M. wochepa. M. mpoto differs from M. wochepa males and females by its longer lower jaw (38.1–42.4 % HL vs. 26.7– 32.5 % in M. wochepa), and from M. lepidiadaptes males by the black submarginal band in its anal fin, which is entirely light blue in fully coloured males of M. lepidiadaptes. In partially coloured males of the latter species the black horizontal stripes are visible, but no vertical bars present, as is the case in M. mpoto. Males of M. mpoto differ from those of M. kaskazini by possessing more teeth in the lower jaw (18–23 vs. 10–16 in M. kaskazini), by having a shallower preorbital depth (15.4 – 20.4 % HL vs. 19.3–26.9 % in M. kaskazini), and by possessing a shallower cheek (15.4–21.7 % HL vs. 19.8 –28.0% in M. kaskazini). Fully coloured males of M. mpoto and M. kaskazini are indistinguishable on the basis of colouration alone, but the basic melanin patterns of the two species, as seen in juveniles and adult females, differ dramatically. Description. Morphometric ratios and meristic values as shown in Table 4. Medium-sized mbuna, spindleshaped body (mean BD 29.8 % SL) with greatest depth at about 9 th to 11 th dorsal spine. Dorsal body profile with gradual curve towards caudal peduncle; ventral body profile straight to slightly convex in females and convex in adult males between pelvic fins and base of rays of anal fin; posteriorly, ventral body profile gradually curving dorsally toward caudal peduncle. Dorsal head profile slightly rounded, with continuous convex curve between interorbital and dorsal-fin origin; horizontal eye diameter (mean 27.7 % HL) considerably greater than cheek depth; approximately ¾ of eye (along horizontal axis) located in anterior half of head; snout elongate and straight with isognathous jaws; tooth bands with 3–4 rows in lower and 3–5 rows in upper jaw, with noticeable gap between first and second row; teeth in anterior outer row equally to unequally bicuspid in females and unequally bicuspid to unicuspid in males; teeth in inner rows mostly unicuspid (some teeth shouldered tricuspid); single series of unicuspid teeth at junction of outer and innermost rows (Fig. 6). Lower pharyngeal bone triangular with moderate posterior indentation; few median teeth slightly enlarged but with pointed tips; other pharyngeal teeth laterally compressed with blade-like, curved tips (Fig. 6). Dorsal fin with XVII or XVIII (mode XVII) spines and 9 or 10 (mode 9) soft rays. Anal fin with III spines and 7 or 8 (mode 8) soft rays. First 4 or 5 dorsal spines becoming gradually longer posteriorly with fourth spine about twice length of first; last 12 spines becoming slightly longer posteriorly with last spine longest, about four times length of first; soft portion of dorsal fin with rounded (females) or rounded to subacuminate (males) tip, fourth or fifth ray longest, reaching base of caudal fin in females and to approximately ¼ length of caudal fin in males. Analfin spines becoming progressively longer posteriorly; fourth or fifth ray longest, reaching base of caudal fin. Caudal fin subtruncate to emarginate. Posterior tip of pelvic fin extending to approximately anal fin in females or to second or third spine of anal fin in large males. Pectoral fin paddle-shaped, posterior tip extending to vertical line through base of 11 th or 12 th dorsal spine. Flank scales large, ctenoid, with abrupt transition to small scales on breast; cheek with 5–7 (mean 6) rows of small scales; 50–75 % of caudal fin covered with tiny scales; no scales present on other fins. Melanochromis mpoto holotype mean range Snout length 34.1 32.9 29.0– 36.8 Postorbital head length 41.0 40.5 39.4 –42.0 ...... continue on next page Colouration. Breeding males: head and body cyan blue. Dorsal fin cyan blue with pale-blue distal margin and white lappets. Caudal fin cyan blue with pale-blue submarginal band and narrow yellow distal margin. Anal fin gray/blue with light-blue distal margin and 3–5 small yellow ocelli. Pelvic fin gray/blue with white/light-blue anterior margin. Pectoral fin with light-gray rays and clear membranes. Full male breeding colour conceals basic melanin pattern typical of females and juveniles. Females: head brown/dark brown with gray/brown gular region. Body bluish-brown/dark brown, often with darker midlateral and dorso-lateral stripes and vertical bars. Dorsal and caudal fins gray/brown with broad yellow posterior edge; anal fin gray/brown with 1–3 tiny yellow spots. Pelvic fin brown with narrow white/light-blue anterior margin. Pectoral fin with brown rays and gray/yellow membranes. Distribution and field observations. Melanochromis mpoto has a wide distribution in the northern part of the lake and has been encountered along the northwestern shore between Chitande Island, near Chilumba, and Nkhata Bay, and on the northeastern shore between Matema and Hongi Island, near Liuli (Fig. 1). Ribbink et al. (1983) also report this species from Likoma Island, but we have not been able to confirm this. Habitat preference and behavior of M. mpoto are similar to those of M. melanopterus in the southern part of the lake. Like the latter species, M. mpoto is a non-specialized, non-territorial cichlid, which lives in rocky and intermediate habitats. Melanochromis mpoto is most often seen at depths of 20– 40 m. It lives a predatory life but has also been seen feeding on plankton. Larger specimens appear to be mainly opportunistic piscivores. Adults are usually solitary but quick to form small “packs” of up to a dozen individuals when hunting opportunities arise. Such packs can contain more than a single male in breeding colouration. These small packs move quickly through the habitat, apparently causing commotion among small prey fishes and invertebrates, and scavenging on anything that seems worth consuming. Stomach content analyses were not performed, but small fishes (fry), invertebrates such as insect larvae, and benthic crustaceans are energetically hunted and certainly part of the diet. Hunting packs are also attracted to disturbed sediment. Territorial males have not been encountered; mouthbrooding females are solitary and sometimes found in water shallower than 10 m. Fry-guarding females have not been seen. Etymology. The specific epithet, a noun in apposition, is derived from ChiTumbuka, the language spoken along the northwestern lake shore, and means “northern,” referring to the distribution pattern of this species.